Japanese Laid-Open Patent Application No. 2005-223882 discusses a data processing method and a data processing apparatus in which a coded digital signal such as a 10 Gigabit Ethernet (registered trademark) is fractionalized in sub-channels having variable granularity, and the sub-channels are mapped in tributaries of a SONET (Synchronous Optical Network)/SDH (Synchronous Digital Hierarchy) path, through a sequential process, i.e., in a cut-through manner not in a store-and-forward manner.